Continuous process for the manufacture of semipulp



u. Pomuo Oct. 31 1939.

' commuous PROCESS FOR THE- MANUFACTURE OF SEMIPULP 5 Sheets-Sheet 1Filed July 16, 1937 +2, INVEN TOR UHBERTQ Pomu Oct. 31, U PQMTLIQ v I vI CONTINUOUS PROCESS FOR. THE MANUFACTURE O sEMIP1Ip P Filed Jul is}1957 5 spegysfs' aefci- I NVENTO R UMBEIETB Iiimuo m'razusys Oct. 31,1939. u. POMILIO 2 6 commuous PROCESS FOR THE MANUFACTURE OF SEIMIPULPFiled July 16, 19:57 5 Sheets-Slfei;

l NVEN TOE UMBERFO Fbrnuo fkMM+M HTTOENEYJ Oct. 31,1939.

,u. POMILIO CONTINUQUS PROCESS FOR THE MANUFACTURE OF SEM-IPULP FiledJuly 16, 1937 l/III/ //II////// I IIIIIII l N V ENTOR UMBERTO Pom/1.10

A TTOEpI s'ys Oct. 31, 1939. u. POMILIO 2.178.266

commuous PROCESS FOR THE MANUFACTURE OF SEMIPULP Filed July 16, 1937 5Sheets-Sheet 5 mvINToR Mnun'fc Riv/1.10

#TTORNEYS 7 a I Patented Oct. 31 1 939 UNITED STATES;

PATElflI "OFFICE CONTINUOUS PROCESS FOR THE MANU- FACTURE OF SEMIPULPUmberto Pomilio, Rome, Italy, assignor to Poj milio Corporation Limited,London, England Application July 16,1937,-seria1 No. 153,995 In GreatBritain Janua y 23. 193'! 1 Claim. (01. 92-13) This invention is forimprovements in or relating to processes and apparatus for theextraction of cellulosic fibres from vegetable material such as thestraws of wheat, barley, rice, rye and J5 other cereals, the stalks offlax, cotton or hemp, canes such as sugar cane, bagasse, Danube canes,bamboo, grasses such as esparto, sisal, tambucki,

Tatching, elephant grass and other wild grasses, A

V 20 making paper pulp tor fine or white papers aim at substantiallycomplete removal of the noncelluloslc materials and these processes arerelatively expensive. There are two well-known methods of produc- 25 ingcheap semipulp. In the Masonite process wood of certain types cut intosmall pieces is subjected in an autoclave to the action of steam underhigh pressur'e'which acts both thermally and chemically on theencrustants of the cellu- 30 lose fibres. When the pressure is suddenlyreleased the loosened vegetable material is broken up into filaments. Inthis process there is no I appreciable removal of the encrustants andthe pulp is of a brown colour. It is used for making 35 boards but isunsuitable for making paper since the pulp is not resolved into separatepapermakers fibres. I I

Mechanical pulp is made by grinding wood with grinding stones (generallythe whiter 40 woods). The wood may be steamed before grinding and againthe steaming operation may result in a certain degree of caramelizationproducing a brown colouration. The power required for the production ofmechanical pulp is high, 45 generally of the order of 1000 kilowatthours -per ton of ground wood or more. Mechanicalpulp contains all the'original encrustants-but the filamentary character of the cellulose isdestroyed. It is not normally used alone for 50 the manufacture-ofpaper. It is employed up to a proportion of about 80% in newsprint(generally in admixture with chemical pulp) and it is employed .in aproportion of 25-40% in many other grades of cheap paper.

.53 In the grinding operation-many of the cellulose fibres arethemselves sub-divided and it is practically impossible in theproduction of mechanical pulp to preserve much of the strength of theoriginal plant filaments. pulp is produced only from wood.

For the manufacture of paper the cellulose Mechanical fibres should, asfar as possible, preserve their original length and quality. It is truethat in the beating engine certain long fibres, such as cotton fibres,are cut to a shorter length but the cellulose fibres which in nature areshort already, such as'those in straws and stalks and wood, should reachthe beater, as far as possible, .in their original length.

Speaking broadly, the problem in the present invention lies in utilisinga wide variety of fibrous vegetable materials (in each localitythecheapest available), in cutting out or cutting down costly operationsor costly materials, and yet producing a semlpulp which can be sent tothe beating engine with the confidence that it will produce marketablepaper.

Fibrous vegetable materials are composed broadly speaking, of cellulosicfibres which are embedded or encrusted in non-cellulosic materialincluding lignins, waxes, resins,,pectic and mucic acids, albuminoidmatter, starchy matter, sugars (like pentosanes) and inorganic matter.

It is already known that the encrusti'ng materials may be removed fromfibrous vegetable matter by treatment with alkali and with chlorine. Thealkali interacts with certain encrusting substances of an acid characteror saponifiable character, such as waxes and resins and the pecticandmucic acids, whilst chlorine reacts with other encrustants,particularly with the lignins to form chloro-lignins and hydrochloricacid, all of which can then be leached out; According to the presentinvention, a process for themanufacture from fibrous vegetable mat 40'ter of semipulp; suitable for paper-makingand cardboard, comprisesreacting on 'the' yeg'etable matter successively with alkali andchlorine gas and is characterizedin that the quantities'of the reagentsemployed are no more than sufiicient to remove a part only' jo thenon-cellulosic constituents and in that the 'zalkali reaction 'iscarried out with the application of heat at atemperature between 75C.'-jand 100 C. and the chlorine reaction is carried out without theapplication of heat.

It is found that the more objectionable noncellulosic constituents canbe attacked by a more dilute reagent than that required to attack theother constituents. 'I'hus,-in carrying out the thermore, the processmay be carried out by so controlling the time over which the reactiontakes place that a predetermined quantity of the non-cellulosicconstituent is rendered capable of removal while the strength of thereagent may be such as to attack any or all of the noncellulosicconstituents.

It has been found that the temperature under which the reactions arecarried out also affects the physical characteristics of the resultingfibre in that high temperature conditions tend to damage the fibre, thefibre being increasingly damaged as the temperature rises above 100 C. Astill more important consideration is that uniformity of resolution isfavoured by carrying out the reactions at low temperature. The reactionswith alkali and with chlorine are exothermic and high temperatures areliable to be built up and accordingly it is a feature of the inventionthat the treatment with alkali and/or with chlorine is not onlyrestricted as regards the extent of removal of non-cellulosicconstituents but also is carried out under conditions which ensure thatthe temperatures built up during a the reactions are sumciently low todiminish damage to the fibre.

A still further feature of the invention consists in that the processcomprises a preliminary stage in which the material is treated with adilute alkali solution, a second stage in which the material is treatedwith chlorine and a third stage comprising a treatment with a verydilute alkali solution. Since these reactions are exothermic, thetemperatures built up are dependent, inter alia, on the velocity atwhich reactions take place and on the rata-at which theevolved heat isdissipated through the material and through the walls of the reactionvessel and accordinglyit maybe desirable to cool the reaction massduring the chlorination and final alkali treatment.

In a process for treatingflbrous vegetable materials with caustic sodaand with chlorine, the cost of the chemicals is a very important item.In the present invention caustic soda may be used in a dilute aqueoussolution (a form of alkali readily obtainable by electrolysis 'of commonsalt solution). A cheap alkali such as soda ash may also be employed.The gaseous chlorine may be used in a moist state diluted with the gasesof the air, a form of chlorine which is likewise very readily producedby electrolysis of salt solution. This invention therefore includes aprocess for the manufacture from fibrous vegetable matter of semi-pulpsuitable for paper-marking in which an aqueous solution of common saltis electrolysed to produce a dilute alkali solution and moist gaseouschlorine and in which the moist gaseous chlorine diluted with air isused for the second stage of the process and the caustic soda solution(at the required concentration) is used for the first and third stagesof the process.

The process in its preferred form comprises three stages, viz:

a,17a,ace

1. A treatment of the fibrous vegetable matter with a solution ofcaustic soda of 1% or less for the removal of a substantial proportionof the acid and saponiiiable encrusting constituents;

2. A treatment of the resulting material with moist chlorine gas dilutedwith air, which treat ment is controlled in the manner set forth above;

3. A treatment of the resulting material with very dilute solution ofcaustic soda of .2% or less.

As already indicated, the amount of caustic soda used during the firstor third treatment and/or the amount of chlorine used during the secondtreatment can be so controlled that these chemical reagents arecompletely used up in attacking a predetermined amount of thenoncellulosic constituents. It is an important practical feature of thisinvention that the vegetable matter receives its chemical treatments ina continuous manner (as distinct from batch treatment), the reactionsbeing carried out successively in separate reaction chambers.

A further feature of the invention consists in that the vegetablematerial is caused to descend under gravity through reaction towers andthat the reagents are introduced at zones near the upper ends oi thetowers. With this arrangement, the vegetable material becomesprogressively consolidated as it descends through the tower and thistends to force the reagents to flow in countercurrent in spite of thefact that in the case of chlorine the gas is heavier than air. By reasonof the downward movement of the vegetable matter, a certain amount ofthe reagents may also be drawn downwardly. In the case of the chlorine,by suitably selecting the point of its introduction into the tower andby controlling its rate of feed and the rate of feed of the vegetablematerial, the chlorine is prevented from reaching either end of thetower before being completely used up in the reaction. Thus there can beno leakage of chlorine into the atmosphere nor are any sealing meansrequired at the ends of the tower.

The velocity at which the reaction takes place in the alkali treatmentis dependent to some extent on the strength of the alkali solutionemployed. I

For treating straw, should it be required to remove the greater part ofthe non-ligneous and non-cellulosic material and to remove about halfthe ligneous non-cellulosic constituents, the strength of the alkalisolution in the preliminary stage is of a concentration up to about 1%.when such a solution is employed, the relative proportions of thereacting substances are selected to be 1 part by weight of vegetablematerial to 3 parts of the solution. The reaction is carried out in anopen vessel without pressure for a period of from 1-4 hours according tothe strength of the solution. The-temperature of the reaction which isexothermic may vary from 75 C. to 100 C. This treatment would result ina reaction with the greater part of the non-ligneous and non-cellulosicconstituents.

The chlorine reaction is also exothermic. Preferably, the chlorine gasis diluted with air and it may be moistened. The reaction mass may alsobe moistened. The chlorine is used in quantities 01' about 4 to 5 partsby weight to 100 parts of the straw, and this will result in thereaction with about one half of the lignepus noncellulosic constituents.About half of the chlorine reacts to form chloro-lignin whilst theremainder of the chlorine is converted into hydro-,

chloric acid and it is advisable that the time during which the fibresare in contact with the drochloric acid, resulting from thechlorination,should be reduced to a minimum since the cellulosic fibres are liable tobe attacked thereby.

An important feature of the invention consists in thatthe chlorinationtreatment and the final alkali treatment are conducted in the cold. Thedilution of the chlorine with air has a dual effect. It reduces thereaction velocity and thus the rate at which heat is evolved, and italso serves toabsorb and conduct away some of the heat; The moisteningof the gas and the reaction mass serves byabsorption to reduceconcentration within-the fibre of the hydrochloric acid which is thereformed and thereby minimises its de1eteri-" ous effect on the fibre. Assoon as chlorination iscomplete the reaction mass is immersed in coldwater. The proportion of air used with the chlorine is dependent on thenature of the vegetable material being treated and it'may vary from to 1part by volume of air to one part by volume of chlorine, whilst themoisture content of the chlorine may be up to its saturation point andthe moisture content of the mass may be two to five times the weight ofthe mass itself.

The proportion of chlorine-air mixture to the vegetable material mayvarywith the nature of the'material being treated, and may vary from 4 to 5parts by weight of chlorine to 100 parts of vegetable material. Thelength '61 chlorination treatment may vary from half-an-hour to threehours by varying the rate .of traverse of the material through theapparatus. The length of the chlorination treatment may vary fromhalf-anhour to three hours.

The compounds formed by these two reactions may not be entirely removedby washing and the third stage, namely, the treatment with a very dilutealkali solution, effects the removal from the material of thosecompounds affected by the first two treatments but still remaining onthe fibres. The strength of the solution employed in this final stagemay be about 1%. The quantity of the solution employed is from 5 to 20parts by weight of solution to, 1 part by weight of the vegetablematerial and the reaction is carried out in the cold.

The following is a description of one form of apparatus for carrying outthe process described above, reference being made to the accompanying,drawings, in which- Figure 1 and Figure 1 taken together represent aside elevation of the plant showing diagrammatically the generalarrangement,

Figure 2 is a vertical section on the line 2-2 of Figure 1 showing thealkali towers in elevation,

Figure 3 is a section through a tower on the line 3-3 of Figure 1,

Figure 4 is an enlarged view of one of the mixing devices of Figure 2,

Figure 5 is an enlarged view of'the mechanism for tilting the hoppernozzle as shown in Figure 4. Figure 6 is a side elevation of the deviceshown inFigure Figure '7 is a plan view of the extractor for thereaction towers.

Figure 8 is an elevation of the arrangement shown in Figure 7.-

Figure 9 is a cross section on the-line9s9 of Figure 8. i

Assuming stalks or straw of plants, such as are referred to at thecommencement of the specification, are to be treated,'these are cut intolengths of a few inches and are loaded into ber l3 open at the top, thelower wall It of which is inclined downwardly from each end to thecentre to form a V. A screw-conveyor I5 is horizontally-disposed alongthe length of'the chamber and has two sets of helical blades arrangedend to end, which blades are oppositely pitched to one another, and aredriven by a motor 22. Disposed above the chamber and at the centrehoppers Ill arranged at the top of the apparatus.

of the screw-conveyor is a V-shaped deflector I6. The hopper is arrangedto deliver the material on to the deflector through a flexible nozotherof the V-shaped deflectorthereby adjusting the relative quantities ofthe material being fed to the two towers. The movement of the nozzle maybe effected by a hand wheel is fixed to a worm shaft is in engagementwith a rack secured to the nozzle. The worm shaft is mounted in abracket 2! secured to the chamber i 5. Caustic soda solution is suppliedto the chambers through a conduit 23 and a suitable device formaintaining a constant level of the solution in the V-shaped recess inthe bottom of the chamber but which level does not. reach the blades ofthe conveyor. As already indicated, the strengthof the solution may be1% or less. Each end of the chamber is open and the screwconveyor forcesthe material mixed with the alkali out through said open ends from whichthe open end of the reaction (as will be seen from Figure 3), thesmaller di-' mension being-about 15 inches and the larger dimension 8feet. The conveyor I3 is so arranged as to effect a mixture of straw andsolution in proportions of one of straw to three of the solution. Steamis introduced through the walls of the tower by a number of pipes 24 ina zone substantially above the horizontal. centre line, e. g.,

'zle I! which may be swung from one side to th 1 one-quarter of thelength from the top. The

steam generating plant 25 and main delivery pipe 26 are shown to theleft of Figure 1. The mass of material-1 gradually descends undergravity and becomes compacted as it descends, and at the bottom forms aseal 'of interlaced fibres which prevent too rapid an escape of theliquid. The time of descent may vary from one to four hours according tothe nature of the material and'the strength of. the caustic solution.Dur ing this time the alkali is almost completely used up to form spentliquor ofav dark colour. The.

tower is provided with inspection windows 9 and sockets 8 forthermometers at different heights. The mass of interlaced fibres isremoved from the bottom of the tower by an extractor 21, the

speed of extraction being adjustable; thus, the

. time of treatment may be varied.

As will be seen from Figures 7 to 9 the extractor comprises two parallelshafts 28 each of which carries a number of star-shaped members 29. Thetwo shafts are rotated through gearing 30 in opposite directions so thatthe arms of the stars draw the material downward and first move towardsone another and then away from one an ther. The mountings for shafts lland the gea g 30 may be so arranged that the distance apart between theshafts may be varied. The gearing may be driven by an electric motor(not-shown) the speed-of which may be controlled thereby controlling therate of withdrawal oi the material from the bottom of the towers.

- The fibres are separated from the spent liquor by a screening device3i through which the material is fed by a screw conveyor 32. Thescreening device is formed in two parts 35, 34 arranged end to end alongthe length of its conveyor and the part at the outlet end 34 receives asupply of wash water through a pipe 35 which wash liquor is delivered byan outlet pipe 35 to a tank 31. The washed and partly-treated fibres are.dellvered by the conveyor through an outlet conduit 38 to a screw-press39 where the remainder of the spent liquor is squeezed out of them anddelivered to a tank 40 through a pipe 4!. The consolidated mass is thenpassed through a conduit 42 to an opener 43 having spiked rollers orcombs where it is converted into a floccular state. It is then raisedbyair blowers 44 through suitable conduits 45 to a receiving chamber 46arranged above the upper end of a set of chlorinating towers 41. Theupper ends of the chlorinating towers are open and the conduits 45 aredirected on to a deflecting plate 48 in the collecting chamber 46whereby the floccular material is caused to fall into the towers.

These. towers may also be about 30 feet in height although those shownin the drawing are shorter. They are of a flattened oval shape incross-section, the general dimensions being the same as those of thealkali towers. Chlorine is introduced into the fibrous mass at a zoneabout 10 feet from the top of each tower. As already indicated the topof each tower is open but the 10 foot column of fibrous material abovethe zone is suillcient completely to absorb the chlorine and preventleakage, and the sealing action is enhanced by the fact that thematerial is descending. The chlorine is introduced into the zone bypipes 49 which extend from a header pipe 50 through the walls of thetower and stop flush with the inside face, and also by means of a set ofpipes 5! which extend downwardly from a header pipe 52. From practicalconsiderations the width between the side walls of the tower cannot bemade much less than 15 inches and since chlorine cannot readilypenetrate the fibrous material to that extent, the additional verticaldelivery pipes are provided. Thus a comparatively small penetration isrequired without the necessity of applying substantial pressure to thechlorine.

Chlorine with the required degree of moisture,

may be prepared in an electrolytic plant 53 from which it passes througha delivery conduit 54 to.

a blower 55 driven by a motor 56. The inlet or suction side of theblower communicates with the atmosphere through a valve 51 and air pipe58. By adjusting the valve 51 a desired quantity of air may be mixedwith the chlorine. The chlorine air mixture is delivered by a pipe 59,to the aforesaid header pipes 49 and 52 through suitable valves 53 and54. The fibrous material gradually sinks through the tower and isremoved from the bottom of the tower by an extractor 55, similar to theaforesaid extractor 21 the speed of extraction being adjustable as inthe case of the alkali tower. .As in the alkali tower inspection windows9 and sockets for thermometers are provided.

The material is then delivered by the extractor into a tank havingrotating stirrers 5| therein through which tank cold water iscirculated. The material passes thence along a trough 82 to a rotatingconical sieve N, the axis of which is horizontal and the angle ofinclination of the walls of which is such as to feed the material fromthe smaller end of the sieve to the larger end. The diluted hydrochloricacid percolates out through the sieve walls into a tank 54 and thefibrous material thus partially freed of acid is passed throughscrew-presses 85 where it is consolidated. The fibrous material is thenpassed through a mixingvat ll' containing a weak solution of causticsoda, e. g., a soda solution of .2% concentration or less. The materialis treated in this vat for afra'ction of an hour and this results inthe-removal oi the chloro-lignin compounds and/or other non-cellulosesoluble matter. Also, any remaining hydrochloric acid or chlorinecombines with the caustic soda. Thereafter the fibres are passed throughthe usual washing and sorting apparatus where knots are removed.

As already indicated the towers both for the alkali and'chlorinetreatments are provided with thermometers so that the predeterminedtemperatures of the reactions may be maintained, for example, bycontrolling the rate of extraction of the material from the bottom ofthe towers. Furthermore, means are provided for periodically testing theair and moisture content of the chlorine mixture.

The starting material may be considered to contain roughly 50%cellulosic constituents and 50% non-cellulosic constituents. Thethree-stage treatment, namely, the first alkali treatment and thechlorine treatment and the final stage, removes the required amount ofthe readily removable constituents and at the same time leaves behind onthe fibres a substantial part of the more desirable non-cellulosicconstituents, especially the ligneous constituents. If the control ofthe chemical treatment is such that only half the non-ceilulosicmaterialis removed, the total yield of solids in the pulp would be about 75% ofthe original weight of vegetable matter. By operating in this manner itwill be appreciated that not only is the time of treatment veryconsiderably reduced but also the consumption of chemicals is very muchless than where the treatment is carried out to remove the whole of theencrusting materials from the cellulosic fibres. The semipulp which isobtained by the process herein described if desired is capable of beingsatisfactorily bleached, satisfactorily treated in the beating engineand may be easily felted to form a good grade of paper. The process,therefore, may be very cheaply operated to produce high-grade semipulp.

I claim:

A continuous process for the manufacture of semipulp from straw whichconsists in mixing the straw with an alkali solution of 1% strength andin proportions of 1 part by weight of straw to 3 parts by weight of thesolution, traversing the mixture through a reaction tower raised to atemperature between 75 C. and C. at such a rate that the materialremains in the tower from 1 to 4 hours, transferring the material to avessel where it is washed with water, dewatering the material andintroducing it with chlorine gas diluted with air in proportions of .5to 1 part by volume of air to 1 part by volume of chlorine and inquantities such that there are 4 to 5 parts by weight of chlorineintroduced to 100 parts by in a cold water bath, transferring the'material POMILIQ. 5

weight of straw, traversing the material at such it with analkalisolution of a strength of .1% and a rate that it remains in the reactionvessel from in quantities from 5 to 20 parts by weight of half an hourtothree hours, immersing the matesolution to 1 part by weight of thevegetable rial, immediately after leaving the last said vessel,material. I

from said bath to another vessel and treating

